when you split vertices, you are physically separating the mesh vertices at the points which exceed the angle you specify..so yes, this does add vertices. However, it will only add vertices to the areas which exceed the angle you specify to split...so this mean you can weld and split all day long and every time you weld it will remove the vertices created by splitting. Usually the default angle is fine, but sometimes you may want to change it (depending on the model). Splitting is done to force hard corners in your mesh so that poser wont smooth the crap out of the areas you dont want smoothed. welding when you first create your model will fix the areas where your modeling program may not export efficiently in the area of "in line" polys (ie vertices that are below the angle you wish to split). Many programs suck quite badly at exporting obj models efficiently. Ive never been clear on the poser weld mesh export option. I never check it so cant help you there. :) BT